Rheumatic heart disease primarily affects which part of the heart?

Rheumatic heart disease primarily affects the heart valves, as it is a complication that arises from rheumatic fever, an inflammatory disease triggered by streptococcal infection. The immune response to the infection can mistakenly attack the body's own tissues, particularly the heart valves. Over time, this can lead to valve stenosis or regurgitation, significantly impacting the heart's function and potentially leading to heart failure.

While the other options refer to important structures in the heart, they are not primarily implicated in rheumatic heart disease. The coronary arteries are responsible for supplying blood to the heart muscle but are not directly affected by rheumatic fever. The myocardium refers to the muscular tissue of the heart that is involved in contracting and pumping blood, which can be impacted by various conditions but is not the primary target of rheumatic fever. Lastly, the pericardium is the protective sac surrounding the heart; although it can be involved in other conditions, it is not specifically affected in rheumatic heart disease. Thus, the heart valves are the main structures impacted in this condition, leading to the correct identification of the affected part of the heart.